Terrestrial planet atmospheres in the aftermath of giant impacts

The final assembly of terrestrial planets is now universally thought to have occurred through a series of giant impacts, such as Earth's own Moon-forming impact. In the aftermath of one of these collisions the surviving planet is hot, and can remain hot for millions of years. The presence of a dense post-impact atmosphere will affect both the cooling of the planet and our ability to detect it. Dr. Lupu will present modeling results regarding the structure, chemistry, and spectral signatures of the atmospheres consisting of vaporized rock material. The atmospheric gas is in equilibrium with the surface magma ocean, with compositions reflecting either the bulk silicate Earth (which includes the crust, mantle, atmosphere and oceans) or the Earth's continental crust as a separate case. Dr. Lupu and her colleagues found that these atmospheres are dominated by H₂O and CO₂, and present characteristic spectral features from HF, HCl, and SO₂. They estimate that cooling timescales for post-giant impact Earths range between about 10^5 and 10^6 years, where the slower cooling is associated with the planet going through a runaway greenhouse stage.

Speaker: Roxana Lupu, SETI